1. Field of the Invention
This invention relates to an automatic car-speed controller suitable to automatically control the traveling speed of a car at a set point by using a small sized-actuator for driving a throttle by a motor.
2. Description of the Prior Art
Heretofore, there have been many types of such automatic car-speed controllers. Among them, there has been an automatic car-speed controller comprising a car-speed sensor for outputting operation data proportional to the actual car-speed, a command switch for outputting a cruise command signal, a car-speed memorizing means for memorizing the operating data from said car-speed sensor in response to an operation of said command switch, an actuator for driving a throttle, and a control means for giving instructions to said actuator in response to the difference between the actual and memorized car-speed.
The actuator of this automatic car-speed controller has been constructed as shown in FIGS. 7 and 8 for example.
Namely, the actuator has a structure wherein a solenoid 106 comprised of an electromagnetic coil 105 is formed in a worm wheel 104 rotatably fitted on a shaft 101 and engaged with a worm 103 of a reduction gear 102. An output pulley 107 rotatably fitted on a shaft 101 is arranged on the upside of the solenoid 106 and the base of the output pulley 107 is provided with an armature 109 connected by a plate spring 108. When the control means actuates the solenoid 106 and rotates a motor 110 in the case of controlling the car-speed, the solenoid 106 attracts the armature 109 against the restoring force of the spring 108, the solenoie 106 is rotated through the reduction gear 102, and the throttle 112 is actuated through the throttle cable 111 attached to the output pulley 107.
However, in the conventional automatic car-speed controller as mentioned above, since the solenoid 106 attracts the armature 109 of the output pulley 107 on the same shaft with the solenoid 106 of the actuator according to the directions from the control means in the case of controlling the car-speed, the output pulley 107 cannot be perfectly synchronized with the solenoid 106 without using a solenoid having a large attractive force. Thus there is a problem in that the thickness of the actuator becomes very large.
In the case of cancelling the system such as during a braking operation, synchronization of the solenoid 106 with the output pulley 107 is released by cutting off the current to the solenoid 106 according to directions from the control means. However, sometimes synchronization of the solenoid 106 with the output pulley 107 cannot be released quickly enough in spite of cutting off the current to the solenoid 106 due to the residual magnetization produced in the armatures 109 because of using a large-sized solenoid 106. Therefore there is a problem in that it is necessary to ensure the safety of the system by rotating the motor 110 in the direction toward the idling position according to directions from the control means.